I agree with MauraP’s plan and typed this similar one up but never posted it:
If you can afford $250/night or more, I would stay at the Boston Marriott Cambridge (which is at MIT/Kendall Square) for multiple nights. I’ve stayed there, it’s nice. You can park there. Be sure to check out the Microsoft NERD center as well, 11th floor (I think) has the best view of the Charles and it’s a great building with a lot going on your kid might be interested in. Free drinks from multiple refrigerators… From there I’d just take the T to BU and Northeastern, and it’s not a bad drive to Tufts, which you can do after you check out, tour, then head to WPI vicinity for the night .
Or, stay at any of the hotels near the Park Street T stop (I would try to Priceline it–Klimpton? Omni?). You’ll be right on the Boston Common and there will be plenty of great restaurants and non-school things to do (movie theater, real theaters, etc). From the Park St stop it’s very easy to take the red line to MIT, the green line to BU, or the red line opposite direction to a quick change to orange line to Northeastern. I say Orange line to Northeastern b/c the Ruggles stop comes out right in the center of campus–so convenient.
All of the schools have parking, it’s just a matter of finding it, actually (you’ll either be lucky or circle and wait, circle and wait), and the parking might not be anywhere near the admissions office, so T or uber/taxi is your best bet. Tufts is hilly with a lot of steps–your H might want to sit that one out. There is a set of intimidating steps from the parking garage to the campus as well. BU, NEU, and WPI are relatively flat. BC-- as long as you’re looking, may as well see that one too-- has some MONSTER steps, however, there’s an elevator somewhere there too if you do decide to see that school as well.
The week before and after the marathon is going to be hell for hotels. Book now. Prices will be very high right before and after Marathon Monday (if there’s even anything left) so you’ll probably want to be gone by the 15th at the latest .
You could also try airbnb.